Bone conduction hearing device



March 14, 1939. E. H. GREIBACH `R 21,030

BONE CONDUCTION HEARING DEVICE Original Filed Nov. ll, 1935 2Sheets-Sheet l ...ad ,w i m v, Mw 3 7. .ww Rm Y l r l 1 f r 1 f a :n 441 m n .Y 5 2 me a R n i/O o m m m 1.! o l N A @u N w IV/fg? ,HE m M mm/M 0 E March 14, 1939. E. GREIBACH BONE CONDUCTION HEARING DEVICEOriginal Filed Nov. 1l, 1955 2 Sheets-Sheet 2 xV/AZZZA INVENTQR EMILHENRY GREI BACH BY liz/MGM ATTORNEY Reissued Mar. 14, 1939 UNITED STATESl Re. 21,030

PATENT OFFICE Original No. 2,127,468, dated August 16, 1938, Se'- rialNo. 697,673, Novemberll, 1933. Reissue No. 20,896, dated October 25,1938, Serial N0.

228,191, September 2. 1938.

This application for reissue December 23, 1938, Serial No. 247,492

61 Claims.

This invention relates to bone-conduction hearing devices and it hasparticular relation to bone conduction receivers for hearing aids oraudiphones.

Among the objects of the invention is abone conduction receiver suitablefor wearable hearing aids that is small enough for inconspicous wear incontact with hearing-inducing bones of the user and is powerful enoughfor imparting tothe bones the vibratory energy required for conductingthe sound vibrations over the bones of the head to the hearing nerves ofthe inner ear and induce hearing.

The foregoing and other objects of the invention will be best understoodfrom the Ifollowing description of the exempliilcations thereofillustrated in the accompanying `drawings in which Flg. l is adiagrammatic view of a wearable bone conduction hearing aid showing abone conduction receiver of the invention worn on the head of a deafenedperson;

Fig. 2 is an enlarged sectional view of a bone conduction receiverexemplifying the invention;

Figs. 3 and 4 are vertical and horizontal sectional views, respectively,along lines 3 3 and l-I of Fig. 2;

Fig. 5 is an enlarged sectional view of another bone conduction receiverexemplifying the invention;

Figs. 6 and 7 are vertical sectional views. respectively, along lines6-6 and 1-1 of Fig. 5,;

Fig. 8 is an enlarged sectional view of another bone conduction receiverexemplifying the invention;

Figs. 9 and 10 are vertical and horizontal sectional views, respectivelyalong lines 9 9 and Ill-I0 of Fig. 8;

Figs. 11 and l2'are sectional views of other types of bone conductionreceivers exemplifying the invention.

It has long been known that the majority of the deafened persons haveimpaired middle ears and can hear much better sound vibrations conductedthrough the bones of the head to the inner ear than sound transmittedthrough the air in the ear canal. However, prior to the presentinvention, only telephone hearing aids which transmitted sound throughair in the ear canal and the middle ear have been available as hearingaids for the deafened. All prior eil'orts to make a bone conductionhearing aid device followed the principles underlying the telephonereceivers and utilized an externally supported heavy stationary drivingmass of a vibratory structure for vibrating a driven vibratory memberusually in the form of a projecting button or rod for imparting to thebones the large-intensity small-amplitude vibrations required forinducing hearing by bone conduction. As a result all prior operativebone conduction hearing devices had to be large, heavy and cumbersome.

The invention overcomes these difllculties by utilizing the principle ofpreservation of the center of gravity of a moving mass system forproducing large-intensity small-amplitude vibrations required forinducing hearing by boneconduction with a light, small vibratorystructure which may be comfortably and inconspicuously worn coupled to abone of the hearing inducing bone body of the user, such as on themastoid bone of the head behind the ear.

accordance with the invention, a relatively small vibratory mass portionis resiliently carried on a hearing inducing bone of the massive body ofthe head of the user to form therewith a vibratory system; and thisvibratory system ls subjected to internal forces induced by electricspeech currents so as to accelerate the resiliently carried vibratoryportion relative to the much larger mass of the head in the inverseratio of their masses and thereby produce inertia reaction forces actingon the bone, proportional to the acceleration and the mass of theresiliently carried vibratory portion, for imparting to the bone thevibratory energy required lfor conducting corresponding vibrations ofrelatively large intensity and small amplitude through the bones to theinner ear and inducing intelligible hearing of speech by boneconduction.

In the practical embodiment of the invention, the resiliently carriedvibratorydriving mass portion is mounted on a substantially rigidbonecoupling vibratcry contact wall portion and so combined ytherewithinto a vibratory unit that when it is placed by an external forceagainst the bone, the vibratory unit automatically assumes astable-equilibrium coupling position along the bone so that a relativelysmall external force is suilicient to maintain the vibratory unit andits resilientlycarried vibratory driving mass portion in efhcientvibration transmitting coupling engagement with the bone, and noprecautions are required to prevent the vibratory unit from tipping orlotherwise breaking its eilicient coupling engagement with the bone.

The stable-equilibrium coupling arrangement of the hearing inducingvibratory unit also assures highly eiilcient transmission of the vibra.-tory energy to the bones because the inertia reaction forces exerted bythe accelerations of the resiliently carried vibratory driving massportion are arranged to act in a general direction substantiallyperpendicular to the predominant dimentality for bringing about theaccelerationof the small resiliently carried vibratory driving massportion relative to the head body in the in'- verse ratio of theirmasses, and thereby translating the electric speech frequencyoscillations i'nto the relatively large-intensity vibrations of smallamplitude which are imparted to the bone for inducing intelligiblehearing of speech by bone conduction. As a result. intelligible hearingby bone conduction is made possible with a light and inconspicuouslysmall vibratory unit, formed essentially of the small vibratory drivingmass portion and its vibratory bone-coupling contact wall portion bymeans of which it is resiliently carried on the bone of the head, and.

having only a small fraction of the mass and volume of the body of head.

Such small bone conduction hearing device of the invention may bedesigned to have a very favorable response characteristic over a widefrequency range, reaching out above the resonance frequency. Itsresponse may be extended down to low frequencies so as to give it a goodresponse over the speech as well as the musical range byv making itsresonant frequency considerably lower than the resonance frequency ofthe telephone-type devices. By a small amount of damping the responsemay be made substantially uniform over the speech and musical frequencyrange.

The low resonance frequency may be secured with a relatively largeeffective stiffness of the rilient spring junction on which the drivingvibratory mass portion is carried by building up the relatively smalldriving mass of all suitable mass elements of the vibratory structure.

The arrangement of the bone conduction receiver described above makes italso possible to shape the bone-coupled driven vibratory contact wallportion so that it forms a protective casing in the interior of whichthe driving vibratory mass portion is resiliently carried in a freelyvibrating condition in which it cannot be disturbed by external forces.As a result, the bone conduction receiver of the invention may be madein the form of a light small casing unit arranged so that when it isplaced by an external force against the bone, its exterior contactsurface automatically assumes a stable-equilibrium coupling positionalong the bone in which it secures efficient transmission of thevibratory hearing inducing energy produced by the resiliently carriedinterior vibratory driving mass portion, which is thus protected againstdisturbance by external forces. d

A wearable bone conduction hearing aid equipped with a bone conductionreceiver exemplifying the principles of the invention is shown in Figs.1 to 4. It comprises a bone conduction receiver shaped in the form of asmall vibrating casing which is held pressed against hearing inducingbones of the user outside the ear canal. for instance, the mastoid bone22, by a resilient head band 2|, of steel, for instance.

lThe casing 20 consists of a rigid base 23 and a rigid cover 2l suitablysecured to the base and engaged by'the head band 2| so as to press thecasing 20 against the bones 22.

The receiver casing 20 is a part of a vibratory structure formed of anelectromagnetic vibrating unit comprising a magnetic. armature core 3|clamped to the base 23 and carrying on a resilient magnetic armaturediaphragm 3 2 a vibratory magnetic core 33 having a central pole piece34 forming with the adjacent face of the armature a small magnetic gap.lThe vibratory structure is actuated with electric audiofrequencycurrent oscillations supplied through terminal bushings 35 provided in aterminal block extending from the base 23 to the actuating windings ofcoil 3G mounted on the pole piece 3| so as to produce a vibratory motionbetween the mass of the resiliently carried vibratory core 33 and thearmature core 3| which is held against the head and forms a part of thecasing 20.

Since the mass of the head is relatively large, it resists the vibratorymotion of the casing, and the smaller resiliently carried vibratory core33 is subjected to vibratory accelerations. As a result, the resilientlycarried vibratory core 33 acts as a driving member and exerts on thearmature core 3| and the casing 20 which is coupled to the hard bones ofthe head inertia reaction forces proportional to the resiliently,carried driving vibratory mass and the acceleration imparted to it bythe electric current oscillation'in the windings of the coil 36. Sincethe casing 2U and armature 3| which is clamped to it are in engagementwith the bones, these inertia reaction forces drive the casing againstthe hard bones and impress on the bones relatively large oscillatoryinertia reaction forces of small amplitude which are conveyed throughthe bones to the hearing nerves where they induce hearing correspondingto the audiofrequency oscillations` impressed on the vibratorystructure.

Although the principles underlying the bone conduction receiver usinganelectromagnetic vibrating structure shown in Figs. 2 to 4, lendsitself for the construction of bone conduction receivers actuated byother types of vibrating structures, electromagnetic vibratingstructures are particularly suitable for use in such bone conductionreceivers because they permit the design of highly eiiicient vibratingstructures with very small magnetic operating gaps of less than onethousandth of an( inch. Such design assures extremely -efficientoperation of electro-magnetic bone conduction receivers, and makespossible the construction of bone conduction receivers of extremelysmall size and relatively large power output required for satisfactoryWearable bone conduction hearing aids.

Inertia reaction bone conduction receivers of the invention constructedwith electromagnetic vibrating structures khave also the furtheradvantage that they may be used as a part of a standard wearable hearingaid worn vhidden in the clothing of the user, by substituting the boneconduction receiver for the air conduction receiver without having toresort to special transformers or other accessories required when suchbone conduction receivers are constructed with other types of vibratingstructures. l

In Fig. 1 is shown how the electro-magnetic j to the same level.

inertia reaction boneconduction receiver of the invention is connectedin the operating circuit of a prior-art wearable hearing aid. Avconventionally illustrated microphone transmitter 46 is connected insexies with a supply battery 4| and a. cut-ofi switch 42 to theactuating coll 43 of a conventionally illustrated amplifier microphone44 which vis connected in series with the battery 4| and the cut-ofiswitch 42 by way of a rheostat 45 to the leads 46 which have terminalplugs engaging the terminal bushings 35 on receiver casing and lead tothe actuating winding 36 of the receiver.

a With such wearable hearing aid assembly, sound waves of the principalaudible frequency range, or, the frequency range of intelligible speech,impinging on the microphone transmitter 4|I will produce in the primarycircuit including the amplifier winding 43 corresponding electricaudlofrequency oscillations and actuate the amplifier microphone 44 toproduce corresponding amplified oscillations which are delivered to theenergizing coilV 36 of the bone conduction receiver which is heldpressed against the bones and transmits through the bones correspondinginertia reaction hearing inducing vibratory forces to the inner ear ofthe user, or his auditory center.

The actual size of the bone conduction receiver shown in Figs. 2 to 4 isonly about onethird the size in which it is shown in the originaldrawings. Its resiliently carried vibratory core 33 is formed of aU-shaped permanent magnet and its central core piece 34 is formed ofsoft iron and secured as by riveting to the center of the core 33. Thepermanent magnet 33 is magnetlzed so that its outer arms are of onepolarity and its center portion to which the core piece 34 is joined ofopposite polarity.

The end surfaces of the two outer core arms of the vibratory core 33have their outer surfaces on the same level as the pole face ofthecentral core 34, their surfaces being preferably ground The armaturediaphragm 32 is made of a magnetically conducting spring steel and hasits center portion stiiened by integrally uniting it, as by soldering orbrazing, to a heavy rigid anchoring cross bar of iron, for instance,extending transversely across the diaphragm 32.

The central portion of the armature diaphragm 32 extends over the fulllength of the cross bar 5I and is integrally united thereto as bysoldering or brazing. The center portion of the anchor bar 5| isprovided with a threaded hole 2|8 in which is threadedly mounted thearmature core 3| having at its exterior end a. slot for turning it toadjust the distance of its pole face from the pole face of the corepiece 34.

'I'he end portions of the cross bar 5| areundercut and fit the sidewalls of a groove provided in the base 23 of the receiver, which may bemolded of a synthetic resin. The cross bar 5| is tightly clamped to thebase 23 by four screws 53 which are screwed into metal anchorers 54,imbedded within the base. An opening in the base 23 is enclosed bysealing plug 55 to give access to the groove of the armature 3| foradjusting the gap. Once the adjustment is made, the armature 3| may belocked `in place, for instance, by a lock member 56. v To the ends ofthe armature diaphragm 32 are united, as by soldering or brazing,reinforcing plates 51 so as to provide a solid clamping joint betweenthe arms of the vibratory core 33 and the ends of the armature diaphragm32.

However. the gap adjustment may be made before the armature supportingbar 5| is clamped to the base and the base may be made with a solidouter surface.

The head band 2| has a detachable universal joint connection with thecover 24. A socket 56 with a lock spring 59 arranged similar to afamiliar snap fastener is embedded in the wall of the cover 24, and ashank 60 extending from the head band has a ball-shaped end which may beinserted into the socket to form with it a detachable universal jointconnection. This universal joint connection assures that, when the headband 2| presses the receiver casing 20 against the bones, the contactsurfaces of the receiver will automatically adjust itself to secure anefficient coupling engagement with the bones in a stableequilibriumcoupling position.

Instead of a head band, any other suitable arrangement for coupling thereceiver structure to the bones may be used.

In manufacturing the bone conduction receiver of Figs. 2 to 4, thevibratory core 33 with the coil 36 and the armature diaphragm 3|32 withthe cross bar 5| may be assembled as a self-contained unit and the gapbetween the armature 3| and the core piece 34 adjusted by turning thearmature 3| until its pole face contacts with the core piece 34.Thereupon the armature 3| is turned back on its thread until a magneticgap of the desired small length is provided between the adjacent polesurfaces and the armature 3| is locked in place. In this adjustedposition the assembled vibrator structure may be tested and after finaladjustment clamped to the .base 23.

A practical bone conduction receiver constructed as shownv in Figs. 3 to4, with the following principal dimensions, will give satisfactoryresults: Permanent magnet core of a total outer length of 1"; a corethickness of a core height of about 1/4"; a core width of about a centercore diameter of about .l"; and a diaphragm thickness of about .014".The magnetic gap is of the order of one thousandth of an inch. Thevibratory permanent magnet core and the center core of the dimensionsgiven above, have a mass of about 8 grams. The foregoing data show thata satisfactory bone conduction receiver of the invention, suitable forinconspicuous wear by the ,user, may be constructed with a drivingvibratory portion having an overall mass which is only a small fractionof the mass of the head.

Because of the relatively large mass of the head, the bone-coupleddriven portion of the receiver will under the action of the vibratoryforces induced by audio-frequency oscillations have only animperceptible vibratory movement and will lbe practically stationarywhile the resiliently carried driving vibratory mass portion will besubjected to audio-frequency accelerations. As a result of thisvibratory movement, relatively large reactive forces will be imparted bythe mass of the resiliently carried vibratory driving core to the bonesof the head, transmitting thereto vibrations of small amplitude andlarge force suicient to convey by bone-conduction speech and music tothe auditory center oi' the head. The magnetic gap is made very small,of the order of a mil or less, thereby securing a high negativestiffness. The armature diaphragm 32 is made of suilcient cross sectionto permit flow of a strong permanent flux through the gap and also topermit inducing strong alternating uxes through the magnet gapby theaction of the sound-frequency current oscillations` passing through theactuating coil. The stiffness of the armature diaphragm is made largeenough to overcome the negative stiilness of the magnetic fluxand securestable vibrations under the action of the fluctuating magnetic eld inthe gap.

By making the joint between the diaphragm 32 and the bar 5l by which itis held clamped to the base solid and firm. as by soldering, the

center portion of the diaphragm strip does not participate in thevibratory movement of the lateral diaphragm portions, eliminatingdistortion that might occur otherwise. By providing at the ends of thediaphragm 32 reinforcing strips I1 which are integrally united with thediaphragm, disturbances due to non-uniform clamping of the diaphragmends are prevented, eliminating distortion.

The high negative stiiness secured by the small magnetic gap enables-theuse of a relatively thick diaphragm 32 having sufficient cross sectionfor carrying the flux while at the same time making its effectivestiffness opposing the negative magnetic stiffness suiliciently small tooperate with a. resonance frequency at which good response is securedover a large sound-frequency range.

In the electromagnetic bone conduction receiver described in connectionwith Figs. 2 to,4, the relatively large resiliently carried vibratorymass of the receiver is utilized to produce the inertia reaction forcesrequired for imparting hearing by bone conduction and a very stiffspring member is utilized to carry the driving vibratory mass so as togive a resonance frequency which assures a good response over the speechfrequency range; The use of such stiff spring makes possible theoperation of the electromagnetic vibrating structure with an extremelysmall magnetic gap distance at which the high ux densities and largemagnetic forces in the gap do not produce fringing or freezing of thepole faces bordering the gap. Such small gaps are made possible by theutilization of the coupled vibratory portion of the vibrating structureas casing which protects the resiliently carried vibratory mass againstany disturbance by external forces. This combination of elements assuresan extremely efficient vibratory structure and. makes possible thedevelopment of relatively large power in a very small receiver unit.

In the bone conduction hearing device described above, thelarge-intensity, small-amplitude forces required for inducingintelligible hearing of Speech by bone conduction are produced with alsmall vibratory unit formed of a driven vibratory portion having aresilient junction carrying a drivingvibratory mass portion that hasonly a small fraction of the mass of the head, and a contact wallsuiiiciently large and so arranged opposite the driving vibratoryportion as to maintain the vibratory unit in a stable-equilibriumcoupling position on the bone with a relatively small external force andcouple by the resilient junction the small mass of the driving vibratoryportionwith the large mass of the head into a. vibrating system having aresonance frequency which gives a good response in the speech frequencyrange and produces by electric speech frequency oscillationsaccelerations of the resiliently carried mass which impart to the bonethe hearing inducing vibratory energy.

Such arrangement makes it possible to use only a small external couplingforce for holding the vibratory unit in its most efllcient hearinginduc- QLS l ing coupling position, particularly since the iny ertiareaction forces which act in a general direction perpendicular to thecontact wall assist in positioning the vibratory unit along the bone. Asa result, no precautions are required to prevent tipping of the bonereceiver unit and a comfortable head-band which is attached to thevibratory Vunit through a loose pivotal universal lioint connectionexerting the small external coupling force makes possible the automaticpositioning of the vibratory unit in its most eilicient,stable-equilibrium, vibration-transmitting coupling position along thebone, and this efllcient coupling engagement is not upset or disturbedby irregularities of the external coupling force.

In Figs. 5 to '1 is shown a bone conduction receiver of the inventionconstructed with a cantilever-type vibratory structure for producing theinertia reaction forces required for inducing hearing by boneconduction. It comprises a vibratory casing, formedr of a rigid base anda cover 1l, held pressed against hearing inducing bones 22 by a headband 2i engaging a channel member formed in the cover 1I. The casinglll- 1I is a pakt of a vibratory structure of the cantilever-type formedof a U-shaped permanent magnet core 12 resiliently carried by a spring13 clamped to a block 14 extending from the base 10, and pole pieces 15extending from the arms of the magnet core 12 to form magnetic gaps witha magnetic armature core 16 clamped to the base of the casing. Avibratory motion is produced between the resiliently carried vibratorymagnet core 12 and the armature 16 with its casing 1li- 1I by actuatingthe vibratory structure with audio-frequency current oscillationssupplied to actuating windings mounted on the pole pieces 15 through theterminal bushings 18 provided in a terminal block extending from thebase 10.

Since the bone-coupled base 10 resists motion and the resilientlycarried driving vibratory core 12 has a substantial mass lrelativelylarge inertia reaction forces will be exerted by the vibratory core 12on the armature 16 and therethrough over the casing to the bones forinducing hearing by bone conduction.

In order to -secure efiicient operation of the vibratory structure witha very tiny gap of.the order of one thousandth of an inch or less, thespring 13 has a longitudinal slot for permitting adjustment of theposition of the resiliently carried vibratory magnet core 12 on thespring 13 so as to assure operation at a minimum gap distance betweenthe pole faces of the pole pieces 15 and the armature 16 without causingfringing of the adjacent pole faces.

In Figs. 8-10 is shown a bone conduction receiver embodying a balancedmagnetic vibratory structure for producing the inertia reactionhearing-inducing vibrations.

It comprises a vibratory casing formed of a base 80 and a cover 8l heldpressed against hearing inducing bones 22 by a head band 2l having auniversal joint connection with the cover 8|, as itil the bone receiverof Figs. 2 to 4. The casing Sil-8| is a part of a vibratory structureformed of a magnetic armature core 82 having its opposite ends clampedto two base projections 83 and resiliently carrying on its magneticdiaphragm extensions 84 a vibratory balanced magnetic core system formedof magnetic core blocks 81 and core bars 85 having central core polepieces 86 facing the opposite faces of the armature BZ'to form therewithtwo magnetic gaps.

a1,oso

The magnetic system ismagnetized so that the two pole pieces 88 are ofopposite polarity and pass a permanent magnetic ilux from one pole piece88 across the armature 82 and its two gaps `to the other pole piece 86,the path of the permanent i'lux being completed by the magnetic coreblocks 81 through which the ends of the opposite magnet bars 88 areclamped to the reinforced ends of the diaphragm 84 without using thediaphragm extensions v84 for carrying the permanent iiux.

n each pole piece 88 are mounted coils oi' actuating windings 88 whichare supplied with electric audioi'requency oscillations through terminalbushings 88 mounted on a terminal block extending from the base 88. Thetwo coils 88 are so connected that when actuated by audiofrequencycurrent oscillations .the ilux in one magnetic gap is reduced while itis increased in the other gap, the diaphragm extensions 86 serving asreturn paths for the alternating iiux. Since the armature 82 is rigidlyclamped to the base 88, the audioirequency flux variations in the twoarmature gaps will produce a vibratory motion between the resilientlycarried vibratory core bars 8l and the amature 82 and the inertiareaction of the resiliently carried vibratory mass will exert on thearmature 82, and therethrough, by way of the casing wall, on the bonesof the user, inertia reaction forces which induce hearing by boneconduction.

To secure emcient ,operation of the magnetic vibrating structure, thecore-pole pieces l86 are threadedly mounted in holes of the magnet bars88 so as to make possible adjustment of the gaps between the pole facesoi the core pieces 86 and the gap faces of the armature 82 at which thegaps will be a minimum without causing fringing of the adjacent polefaces during the operation of the receiver. Lock nuts provided on theexterior threaded ends oi.' the core pole pieces 88 permit locking ofthe pole pieces 86 in their adjusted positions.

By using a balanced magnetic system in the bone conduction receiver ofthe invention, of the type shown in Figs. 8 to 10, even harmonicdisiortion'is eliminated and objectionable saturation of the nuxpaths isavoided.

Since the permanent iiux acting on the opposite pole faces of theamature is balanced, the armature diaphragm is not subjected to anypermanent deflection. Furthermore,'the maximum amplitude of thevibrations between the armature and the vibratory core is limited by thesmall magnetic gaps of the order of one thousandth of an inch on theopposite sides of the armature.

Accordingly, flexing oi.' the armature diaphragm beyond its elasticlimit is prevented, and even if the receiver is dropped, and themomentum of the .heavy vibratory mass tends to impart a large deilectionto the armature diaphragm, this deection will be limited by the smallgaps on the opposite sides oi' the amature toa value at which theelasticity oi' the diaphragm will laummatically restore the normal gapspacing.

As a result, the receiver may be dropped without damage, and it may beoperated with smaller gaps than receivers without balanced magnetic coresystems, thereby increasing its eiliciency.

In Figs. 11 and 12 are shown two other exempliiicatlons of an inertiareaction bone conduction receiver of the invention. In the arrangementof Fig. 1l, a receiver housing formed of a casing 86 and a top wall 8|has clamped to the top wall 8l an extension of a magnetic core piece 82on which is mounted a magnetic diaphragm 88 resiliently carrying avibratory U-shaped magnet core 8l which has a central pole face forminga magnetic gap with the pole face of the core piece 82. The vibratorystructure is actuated by a coil 86 mounted on the core piece 82 clampedto the top 8| of the casingto produce under the action of audiofrequencycurrents a vibratory motion between the resiliently carried vibratorycore 86 and thecore piece 82. As a result, the inertia reaction of theresiliently carried vibratory core exerts hearing inducing vibratoryforces on the core piece 82 and therethrough, over the casing 88 on thehearing-inducing bones engaged by the casing.

The casing of the bone conduction receiver shown in Fig. 1.1, isillustrated in the form of a .bridge member of a spectacle frame and itsexterior walls are shown curved to form a concave contact surface forsecuring intimate coupling engagement with the bones 22 of the nose andsecurean eiiicient transmission of the hearing-inducing vibratory energyfrom the receiver casing to the bones.

In the arrangement oi' Fig. 12 is shown an inertia reaction boneconduction receiver of the invention having an electromagnetic vibrating.structure similar to that shown in Figs. 2 to 4. It

comprises a vibratory magnetic core 33 resiliently carried by anarmature diaphragm 32 which is clamped to a wall of an enclosing casing86 having a projecting contact member 81 with a curved concave contactsurface held in engagement with hearing inducing bones 22 of the user.This bone conduction receiver is likewise designed for mounting in abridge member of a spectacle frame 88 forming a housing around thereceiver casing 86 and supporting it between two springs 88 so as toprevent the vibrations of the receiver casing 86 which are transmittedby the contact member 81 to the bones of the nose from being transmittedto the spectacle frame 88.

The performance and the quality oi' the reproduction in the boneconduction receivers of the invention described above may be increasedwithout increasing their weight and size by employing instead ofordinary steel diaphragms special materials of high magneticpermeability, such as Hypernik, A-metal or Permalloy. These materialshave a much higher magnetic permeability than ordinarily used springsteel. They accordingly reduce the flux reluctance and enabledevelopment oi' larger iiuxes increasing thepower output of a given sizeand weight of structure.

In the lbone conduction receivers described above,.such highpermeability materials may be used notwithstanding their relativelysmaller elasticity, because the small amplitudes with which thediaphragme are required `to operate produce only small strains in suchdiaphragms, and thesestrains are within their elasticity limits. Byusing such materials for diaphragms, they may be given a relativelygreat thickness without unduly increasing their stiffness, thusproviding a large cross vsection ofhighly permeable magnetic materialfor producing a large flux and providing at the same time the requiredelasticity for operating with a desirable degree of stillness.

The principles of the invention described above in connection withvarious types of electromagnetic vibrating structureswill suggestto'those skilled in the art manyother ways of making small inertiareaction'bone conduction receivers with various other types ofelectrically actuated vibratory structures which are generally used forconstructing telephones, loudspeakers and similar acoustic devices. Itis accordingly desired that the appended claims be given a broadconstruction commensurate with the scope of the invention within theart.

I claim:

1. In a bone conduction hearing aid device suitable for inconspicuouswear by a deafened person, an elastically deformable vibratory mem- 10ber having two vibratory portions and means for actuating said vibratorymemberA with electric oscillations substantially throughout the speechfrequency range for producing corresponding vibrations of said vibratoryportions, one of said i6 vibratory portions having a contact surfacearranged to be held coupled under pressure to hearing inducing bones ofthe user and resiliently carrying the other of said vibratory portions,the resiliently carried vibratory portion having sumcient mass andexerting under the action of the elastic oscillations suillcient inertiareaction forces upon the coupled vibratory portion and therethrough uponthe coupled bones of the user for,

imparting thereto the vibratory energy required 26 for conductingcorresponding vibrations through the bones to the inner ear ofthe userand induce intelligible hearing.

2. In a bone conduction hearing device suitable for inconspicuous wearby a user, a vibratory 30 structure having a driving magnetic coremember anda driven magneticcore member resiliently joined into amagnetic ilux path including a gap,

means for holding said driven core member coupled under pressuretohearing inducing bones of the user outside the ear canal and carryingsaid .driving core member in a vibrating condition, and

windings interlinked with vsaid ux path for actuating said vibratorystructure with electric oscillations of the principal audible frequencyrange 0 to produce corresponding vibrations of said core members acrosssaid gap, said driving core member having a suillciently large mass andexerting under the action of the electric oscillations sumcient inertiareaction forces upon said driven core 46 member and therethrough uponthe coupled bones for imparting thereto the vibratory energy requiredfor conducting corresponding vibrations through the bones to the innerear and induce intelligible hearing. y'

60 3. The method of enabling a deafened person to hear speech throughbone conduction by imparting audio-frequency vibrations to a bone of themassive head body surrounding his inner ears which resides in soresiliently carrying in a vibra- '65 tory condition and in astable-equilibrium coupling position on the bone a vibratory portionhaving a mass that is smaller than about two hundred grams and only asmall` fraction of the Vmass of the head body but greater than aboutfour 50 grams that the large mass of the body and the small mass of theresiliently carried vibratory portion form a. vibrating system having ares'onance frequency which gives a good response in the speech frequencyrange, and accelerating the resiliently carried vibratory portionrelativeto the bone with electric oscillations of the principal speechfrequency range so as to produce by the acceleration of the reslientlycarried vibratory mass portion inertia reaction forces which impart tothe bone the vibratory energy required for conducting correspondingvibrations of relatively large intensity and small amplitude through thebones to the inner ear and induce intelligible u hearing of the speech.

4. The method of enabling a deafened person to hear speech through boneconduction by imparting audio-frequency vibrations to a bone of themassive head body surrounding his inner ears which resides in soresiliently carrying in a freely 5 vibratory condition and in astable-equilibrium coupling position on the bone a vibratory electro-`magnetically actuated portion having a mass that 'iis smaller thanabout two hundred grams and only a small fraction of the mass of thehead body l0 but greater than about four grams that the large mass ofthe body and the small mass of the resiliently carried vibratoryportionform a vibrating system having a resonance frequency which gives a goodresponse in the speech frequency range, l5 and accelerating theresiliently carried vibratory portion relative to thebone with electricoscillations of the principal speech frequency range so as to produce bythe acceleration of the resiliently carried vibratory mass portioninertiav reaction 20 forces which impart to the bone the vibratoryenergy required for conducting corresponding'vlbrations of relativelylarge intensity and small amplitude through the bones to the inner earand induce intelligible hearing of the speech. 25

5. In a wearable bone conduction hearing aid device, a vibratory unitdesigned and arranged to be sulciently light and small for comfortableand substantially' inconspicuous wear coupled to a hearing inducing boneoutside the ear canal of 30 the massive body of the head surrounding theinner ears of the user comprising: a driving vibratory portion having amass greater than about three grams, which is only a small fraction ofthe mass of said body; a driven bone-coupling $6 vibratory portionhaving a resilient Junction carrying said driving portion in a vibratorycondition and arranged to operatively couple said small-mass drivingportion with the large-mass body by the resilient junction into avibratory 40 system; said vibratory unit having a wall portion withlateral dimensions of the order of the lateral dimensions of the drivingvibratory portion or greater, sufllciently large and so arrangedthereunder as to maintain said vibratory unit in a stable-equilibriumcoupling position on the bone' under a relatively small external forcefor eiliciently transmitting to the bone the vibratory forces exerted bythe vibratory unit; and means for actuating said vibratory portions withelectric oscillations throughout the principal speech frequency rangefor producing corresponding vibrations of said vibratory portions acrossthe space between said vibratory portions; the mass of the drivingvibratory portion and the stillness of its resilient junction being soproportioned and so arranged in the vibratory unit that the vibratorysystem which they form with the mass of said body has a resonancefrequency which gives a good vibratory response in the speech frequencyrange, and that the mass of the resiliently carried driving vibratoryportion is sufilciently large and subjected by the oscillations tosuillcient acceleration relative to the bone so that the drivingvibratory portion exerts inertia reaction forces in a e5 generaldirection toward the wall portion surface required for imparting to thedriven vibratory portion and therethrough to the bone vibrations oflarge intensity and small amplitude required for inducing intelligiblehearing of speech by bone conduction.

6. In a wearable bone conduction hearing aid device, a vibratory unitdesigned and arranged to be suflciently light and small for comfortableand substantially inconspicuous wear coupled to a 75 hearing inducingbone outside the ear canal of the massive body of the head surroundingthe inner ears of the user comprising: a driving vibratory portionhaving a mass greater than about three grams, which is only a smallfraction of the mass of said body; a driven bone-coupling vibratoryportion having a resilient junction carrying said driving portion in avibratory condition and arranged to operatively couple said small-massdriving portion with the large-mass body by the resilient Junction intoa vibratory system; said driven vibratory portion forming a part of awall portion with lateral dimensions of the order of the lateraldimensions of the driving vibratory portion or greater, suilicientlyextended and so arranged thereunder as to maintain said vibratory unitin a stable-equilibrium coupling position on the bone under a relativelysmall external force for efficiently transmitting to the bone thevibratory forces exerted by the vibratory unit; and means for actua'lingsaid vibratory portions with electric oscillations throughout theprincipal speech frequency range for producing corresponding vibrationsof said vibratory portions across the space between said vibratoryportions; the mass of the driving vibratory portion and the stiffness ofits resilient junction being so proportioned and so arranged in thevibratory unit that the vibratory system which they form with the massof said body has a resonance frequency which gives a. good vibratoryresponse in the speech frequency range, and that the mass of theresiliently carried driving vibratory portion is sufilciently large andsubjected by the oscillations to suillcient acceleration relative to thebone so that the driving vibratory portion exerts inertia reactionforces in a general direction toward the wall portion surface requiredfor imparting to the driven vibratory portion and therethrough to A thebone the vibrations of large intensity and small ampliude required forinducing intelligible hearing of speech by bone conduction, said wallportion forming part of a casing enclosing said driving vibratoryportion.

7. In a wearable bone conduction hearing aid device, a vibratory unitdesigned and arranged to be suillciently light and small for comfortableand substantially inconspicuous wear coupled to a hearing inducing boneoutside the ear canal of the massive body of the head surrounding' theinner ears of the user comprising: a driving vibratory portion having amass greater than about three grams, which is only a small fraction ofthe mass of said body; a driven bone-coupling vibratory portion having aresilient junciion carrying said driving portion in a vibratorycondition and arranged to operatively couple said small-mass drivingportion with the large-mass body by the resilient junction in to avibratory sysem; said vibratory unit having a wall portion with lateraldimensions of the order of the lateral dimensions of the drivingvibratory portion or greater, sulficiently large and so arrangedthereunder as to maintain said vibratory unit in a stable-equilibriumcoupling position on the bone under a relatively small external forcefor emciently transmitting to the bone the vibratory forces exer'ed bythe vibratory unit; and means for actuating said vibratory portions withelectric oscillations throughout the principal speech frequency rangefor producing corresponding vibrations of said vibratory portions acrossthe space between said vibratory portions; the mass of the drivingvilzratory portion and the stiifness of its resilient Junction being soproportioned and so arranged in the vibratory unit that the vibratoryksystem which they foi-m with the mass of said body has a resonancefrequency which gives a good vibratory response in the speech frequencyrange, and that the mass of the resiliently carried driving vibratoryportion is sufficiently large and subjected by the oscillations tosucient acceleration relative to the bone so that the driving vibratoryportion exerts inertia reaction forces in a general direction toward thewall portion surface required for imparting to the driven vibratoryportion and therethrough to the bone vibrations of large intensity andsmall amplitude required for inducing intelligible hearing of speech bybone conduction, and external supporting means having a ,surrounding theinner ears of the user comprising: a driving vibratory magnetic coremember having a mass greater than about four grams,

and smaller than, about two hundredgrams so that it is only a smallfraction of the mass of said body;A a driven bone-coupling vibratorymagnetic core member having a resilient junction carrying said drivingcore member in a vibratory condition to form therewith a magnetic pathincluding a gap and arranged to op.- eratively couple saidsmall-massdriving member with the large-mass body by the lresilientjunction into a vibratory system; said vibratory unit hav# ing asubstantially rigid wall portion sumciently large and so arranged underand relatively to the' driving vibratory member as to maintain saidvibratory unit in a stable-equilibrium coupling position on the boneunder a relatively small external coupling force for efficientlytransmitting to the bone the vibratory forces exerted by the vibratoryunit; and means including windings for actuating said vibratory coremembers with electric oscillations throughout the prin cipal speechfrequency range for producing corresponding vibrations of said vibratorymem-- bers across said gap; the mass of the driving vibratory member andthe stiffness of its resilient junction being so proportioned and soarranged in the vibratory unit that the vibratory system which they formwith the mass of said body has a resonance frequency which gives a goodvibratory response in the speech frequency range, and that the mass ofthe resiliently carried driving vibratory member is sumciently large andsubjected by the oscillationsto suilcient acceleration relative to thebone so that the driving vibratory member exerts on the driven vibratorymember and therethrough on the bone inertia reaction forces required forinducing intelligible hearing of speech by bone conduction.

9. In a wearable bone conduction hearing aid device, a vibratory unitdesigned and arranged to be sufficiently light and small for comfortableand substantially inconspicuous wear coupledv to a hearing inducing boneof the massive body surrounding the inner ears of the user comprising: adriving vibratory magnetic core member having a mass greater than aboutfour grams,

and smaller than about Vtwo hundred grams so.,

that it is only a small fraction of the mass of said body; a drivenbone-coupling vibratory magnetic core member having a resilient junctioncarrying said driving core member in a vibratory condition to formtherewith a magnetic path including a gap and arranged to operativelycouple said small-mass driving member with the large-nass body by theresilient junction into a vibratory system; said vibratory unit having asubstantially `-rigid wall portion suiliciently large and so arrangedunder and relatively to the driving vibratory member as to maintain saidvibratory unit in a stable-equilibrium coupling position on the boneunder a relatively small external coupling force for emcientlytransmitting to the bone the vibratory forces exerted by the vibratoryunit; and, means including windings for actuating said vibratory coremembers with electric oscillations throughout the principal speechfrequency range for producing corresponding vibrations of said vibratorymembers across said gap; said vibratory .unit having a closure portionarranged to protectively isolate from the exterior the space acrosswhich said vibratory members vibrate; the mass of the driving vibratorymember and the stiffness of its resilient junction being so proportionedand so arranged in the vibratory unit that the vibratory system whichthey form with the mass of said body has a resonance frequency whichgives a good vibratory response in the speech frequency range. and thatthe mass of the resiliently carried driving vibratory member issumciently large and subjected by the oscillations to suilicientacceleration relative to the bone so that the driving vibratory memberexerts on the driven vibratory member `and therethrough on the boneinertia reaction forces required for inducing intelligible hearing ofspeech by bone conduction.-

10. In a wearable bone conduction hearing aid device, a vibratory unitdesigned and arranged to be suiciently light and small for comfortableand substantially inconspicuous wear coupled to a hearing inducing boneof the massive body surrounding the inner ears of the user comprising: adriving vibratory portion having a mass greater than about four grams,and smaller than about two hundred grams so that it is only a smallfraction of the mass of said body; a driven bone-coupling vibratoryportion having a resilient junction carrying said drivingportion in avibratory condition and arranged to operatively couple said small-massdriving portion with the large-mass body by the resilient junction intoa vibratory system; said vibratory unit having a substantially rigidwall portion sufliciently large and so arranged under and relatively tothe driving vibratory portion as to maintain said vibratory unit in astable-equilibrium coupling position on the bone under a relativelysmall external coupling force for efficiently transmitting to the bonethe vibratory forces exerted by the vibratory unit; `and means foractuating said vibratory portions with electric oscillations throughoutthe principal speech frequency range for producing correspondingvibrations of said vibratory portions across the space between saidvibratory portions; the mass of the driving vibratory portion and thestiiness of its resilient junction being so proportioned and so arrangedin the vibratory unit that the vibratory system which they form with themass of said body has a resonance frequency which gives a good vibratoryresponse in the speech frequency range, andy that the mass of theresiliently carried driving vibratory portion is suiliciently large andsubjected by the oscillations to suiiicient acceleration relative'to thebone so that the driving to a hearing inducing bone outside the earcanal of the massive body of the Ahead surrounding the inner ears of theuser comprising: a driving vibratory portion having a mass greater thanabout four grams, and smaller than about two .hundred grams so that itis only a small fraction of the mass of said body; a driven bonecouplingvibratory portion having a resilient junction carrying said drivingportion in a vibratory condition and arranged to operatively couple saidsmall-mass driving portion with the large-mass body by the resilientjunction into a vibratory system; said vibratory unit having asubstantially rigid wall portion sufliciently large and so arrangedunder and relatively to the driving vibratory portion asv to maintainsaid vibratory unit in a stable-equilibrium coupling position on thebone under a relatively small external coupling force for eflicientlytransmitting to the" bone the vibratory forces exerted by the vibratoryunit; and means for actuating said vibratory portions with electricoscillations throughout the principal speech Ifrequency range forproducing corrponding vibrations of saidv vibratory portions across thespace between said vibratory portions; the mass of the driving vibratoryportion and the stillness of its resilient junction being soproportioned and so arranged in the vibratory unit' that the vibratorysystem which they form with the mass of said body has a resonancefrequency which gives a good vibratory response in the speech frequencyrange, and that the mass of the resiliently carried driving vibratoryportion is sumciently large and subjected by the oscillations tosuilcient acceleration relative to the bone so that the drivingvibratory portion exerts on the driven vibratory portion andtherethrough on the bone inertia reaction forces required for inducingintelligible hearing of speech by bone conduction, and externalsupporting means having a pivotal joint connection with said vibratoryunit for holding said wall portion cooperatively coupled to the bone.

l2. In a wearable bone conduction hearing aid device, a vibratory unitdesigned and arranged to be sufficiently light and small for comfortableand substantially inconspicuous wear coupled to a hearing inducing boneof the massive body surrounding the inner ears of the user comprising: adriving vibratory portion having a mass greater than about four grams,and smaller than about two hundred grams so that it is only a smallfraction of the mass of said body; a driven bone-coupling vibratoryportion having a resilient junction carrying said driving portion in avibratory condition and arranged to operatively couple said small-massdriving portion with the large-mass body by the resilient junction intoa vibratory system; said vibratory unit having a substantially rigidwall portion suiliciently large and so arranged under and relatively tothe driving vibratory portion as to maintain said vibratory unit in astable-equilibrium coupling position on the bone under a relativelysmall external coupling force for eiliciently transmitting to the bonethe vibratory 7| forces exerted by the vibratory unit: and means foractuating r.id vibratory portions with electric oscillationsthroughoutthe principal speech frequency range for producing correspondingvibrations of said vibratory vportions across the space between saidvibratory portions; said vibratory unit having a closure portionarranged to protectlveiy isolate from the exterior the space acrosswhich saidvibratory portions vibrate: the mass ol the driving vibratoryportion and the .stiffness of its resilient iimction being soproportioned and so arranged in the vibratory unit that the-vibratorysystem which they` form with the mass oi' said body has a resonanceyfrequency which gives a good vibratory response in the speech frequencyrange, and that the mass of the resiliently carried driving vibratoryportion is suillciently large and subjected by the oscillations tosuflicient'acceleration relative tc the bone so that the drivingvibratory portion exerts on the driven vibratory portion andtherethrough on the bone inertia reaction forces required for inducingintelligible hearing of speech bybone conduction.

i3. In a wearable bone conduction hearing aid device, a vibratory unitdesigned and arranged to be sufficiently light and small for comfortableand substantially inconspicuous wear coupled to a hearing inducing boneof the massive body surrounding the inner ears of the user comprising: adriving vibratory portion having a mass greater than about four grams,and smaller than about one hundred and sixty grams so that it is only asmall fraction of the mass of said body; a driven bone-'couplingvibratory portion having a resilient Junction carrying said drivingportion in a vibratory condition and arranged to operatively couple saidsmall-mass driving portion with the large-mass body by the resilientjunction into a vibratory system; said driven vibratory portion forminga part of a wall portion suillciently extended and -so arranged underand relatively to the driving vibratory portion as to maintain saidvibratory unit in a. stable equilibrium coupling position on theboneunder a relativelyv small external coupling force for efiicientlytransmitting to the bone the vibratory forces exerted by the vibratoryunit; and means for actuating said vibratory portions with electricoscillations throughout the principal speech frequency range forproducing corresponding vibrations of said vibratory portions across thespace between said vibratory portions;the mass of the driving vibratoryportion and the stiffness of its resilient junction being soproportioned and so arranged in the vibratory unit that the vibratorysystem which they form with the large mass of said body has a resonancefrequency which gives a good .vibratory response in the speech frequencyrange, and that the mass of the resiliently carried driving vibratoryportion is sumeienuy large and subiected by the osculations tosufficient acceleration relative to the bone so that' the drivingvibratory portion exerts inertia reaction forces required for impartingto the driven vibratory portion and therethrough to the bone vibrationsof large intensity and small amplitude required for indlmingintelligible hearing of speech by bone conduction.l

i4. -In a wearable bone conduction hearing aid device, a vibratory unitdesigned and arranged to be sufficiently light and small for comfortableand substantially inconspicuous wear coupled to a hearing inducing boneoutside the ear canal of the massive body of the headsurroundingtheinnerearsoftheusercomprlsing: a driving vibratory portionhaving a mass greater than aboutAfour grams, and smaller than about onehundred and sixty grams so that it is only a small fraction of the massof said body; a driven bone-coupling vibratory portion having aresilient Junction can'ying said driving portion in a vibratorycondition and arranged to operatively couple said small-mass drivingportion with the large-mass body by the resilient Junction into avibratory system; said driven vibratory portion forming a part of a wallportion suiliciently ,A extended and so'arranged under and relatively tothe driving vibratory portion as to maintain said vibratory unit in astable-equilibrium coupling position on the boneunder a relatively smallexternal coupling force for efficiently transmitting to the bone thevibratory forces exerted by the vibratory unit; and means for actuatingsaid vibratory portions with electric oscillations throughout theprincipal speech frequency range for producing corresponding vibrations'of said vibratory portions across the space between said vibratoryportions the mam of the driving vibratory portion and the stinness ofits resilient junction being so proportioned and so arranged in thevibratory unit that the vibratory system which they form with the largemass of said body has a resonance frequency 'which gives a goodvibratory response in the speech frequency range, and that the mass ofthe resiliently carried driving vibratory portion is sumciently largeand subjected bythe oscillations to sufllcient acceleration relative tothe bone so that the driving vibratory portion exerts inertia reactionforces required for imparting to the driven vibratory portion andtherethroughto the bone vibrations of large intensity and smallamplitude required for inducing intelligible hearing of speech by boneconduction, and external supporting means having a pivotal Jointconnection with said vibratory unit for holding said wall portioncooperatively coupled to the bone.

15. In a wearable bone conduction hearing aid device, a vibratoryunitdes'igned and arranged to be sufficiently light and small forcomfortable and substantially inconspicuous wear coupled to a hearinginducing bone of the massive body surrounding the inner ears of the usercomprising: a driving vibratory portion having a mass greater than aboutfour grams. and smaller than about one hundred and sixty grams so thatit is only a small fraction of the mass of said body: a drivenbone-coupling vibratory portion having a resilient junction carryingsaid driving portion in a vibratory condition and arrangedto operativelycouple said small-mass driving portion with the large-mass body by theresilient Junction into a vibratory system:said driven vibratory portionforming a part of a wall portion sumciently extended and so arrangedunder and relatively to theA driving vibratory portion as to maintainsaid vibratory unit in a stable-equilibrium coupling position on thebone under a relatively small external coupling force for efilcientlytransmitting to the bone the vibratory forces exerted by the vibratoryunit: and means for actuating said vibratory portions with electricoscillations throughout the principal speech frequency range forproducing corresponding v1- bations of said vvibratoryportions'acrosathe space between said vibratory portions: said vibratoryunit having a closureportion arranged to protectively isolate from theexterior the space across which said vibratory portions vibrate; themass of the driving vibratory portion and the stiifne of its resilientjunction being so proportioned and so arranged in the vibratory unitthat the vibratory system which they form with the large mass of saidbody has a resonance frequency which gives a good vibratory response inthe speech frequency range, and that the mass of the resiliently carrieddriving vibratory portion is sufllclently large and subjected by theoscillations to sufllcient acceleration relative to the bone so that thedriving vibratory portion exerts inertia reaction .forces required lforimparting to the driven vibratory portion and therethrough to the bonevibrations of large intensity and small amplitude required .for inducingintelligible hearing of speech by bone conduction.

16. In a wearable bone conduction hearing aid device, a vibratory unitdesigned and'arranged to be sufnciently light and small for comfortableand substantially inconspicuous wear coupled to a hearing inducing boneof the massive body surrounding the inner ears of the user comprising: adriving vibratory magnetic core member having a mass greater than aboutfour grams, and smaller than about one hundred and sixty grams so thatit is only a small fraction of the mass of said body; a drivenbone-coupling vibratory magnetic core member having a resilient junctioncarrying said driving core member in a vlbratory condition to formtherewith a magnetic path including a gap and arranged to operativelycouple said small-mass driving member with' the large-mass body by theresilient junction into a vibratory system; said driven vibratory memberforming a part of a wall portion suiilciently extended and so arrangedunder and relatively to the driving vibratory member as to maintain saidvibratory unit in a stable-equilibrium coupling position on the boneunder a relatively small external coupling force for eilicientlytransmitting to the bone the vibratory forces exerted by the vibratoryunit; and means including windings for actuating said vibratory coremembers with electric oscillations lthroughout the principal speechfrequency range for producing corresponding vibrations of said vibratorymembers across said gap; the mass of the driving vibratory member andthe stiffness of its resilient junction being so proportioned and soarranged in the vibratory unit that the vibratory system which they formwith the large mass of said body has a resonance frequency which gives agood vibratory response in the speech frequency range, and that the massof the resiliently carried driving vibratory member is sufficientlylarge and subjected by the oscillations to sumcient accelerationrelative to the bone so that the driving vibratory member exerts inertiareaction forces required for imparting to the driven vibratory memberand therethroughy to the bone vibrations of large intensity and smallamplitude required for inducing intelligible hearing of speech by boneconduction.

17. In a wearable bone conduction hearing aid l device, a vibratory unitdesigned and arranged to be suillciently light and small for comfortableand substantially inconspicuous wear coupled to a hearing inducing boneof the massive body surrounding the inner ears of the user comprising: adriving vibratory magnetic core member having a mass greater than aboutfour grams, and smaller than about one hundred and sixty grams so thatit is only a small fraction of the mass of said body; a drivenbone-coupling vibratory. magnetic core member having a resilientjunction carrying said driving `core member in a vibratory condition toform therewith a magnetic path including a gap and arranged tooperatively couple said small-mass driving member with the large-massbody by the resilient junction into a vibratory system; said drivenvibratory member forming a part of a wall portion sumcientlyextended andso arranged under and relatively to the driving vibratory member as tomaintain said vibratory unit in a stable-equilibrium coupling positionon l the bone under a relatively small. external coupling force forefilclently transmitting to the bone the vibratory forces exerted by thevibratory unit; and means including windings for actuating saidvibratory core members with electric oscillations throughout theprincipal speech frequency range for producing coresponding vibrationsof said vibratory members across said gap; said vibratory unit having aclosure portion arranged to protectively isolate from the exterior thespace across which said vibratory members vibrate; the mass of thedriving vibratory member and the stiffness of its resilient junctionbeing so proportioned and so arranged ln the vibratory unit that thevibratory system which they form with the large mass of said body has aresonance frequency which gives a good vibratory response in the speechfrequency range, and that the mass of the resiliently carried drivingvibratory member is sufllciently large and subjected by the oscillationsto sufhcient acceleration relative to the bone so that the drivingvibratory member exerts inertia reaction forces required for impartingto the driven vibratory member and therethrough to the bone vibrationsof large intensity and small amplitude required for inducingintelligible hearing of speech by bone conduction.

18. In a wearable bone conduction hearing aid device, a vibratorystructure designed and arranged to be suiliclently light and small forcomfortable and substantially inconspicuous wear coupled to a hearinginducing bone of the massive body surrounding the inner ears of the usercomprising: a driving vibratory portion having a mass greater than aboutfour grams, andsmaller than about one hundred and twenty grams so thatit is only a small fraction of the massof said body; a drivenbone-coupling vibratory portion having a resilient junction carryingsaid driving portion in a vibratory condition and arranged tooperatively couple said small-mass driving portion with the large-massbody by the resilient junction into a vibratory system; said drivenvibratory portion forming a part of a wall portion with lateraldimensions of the order of the lateral dimensions of the drivingvibratory portion or greater. sumciently large and so arranged oppositethereto as to maintain said vibratorystructure in a stableequilibriumcoupling position on the bone under a relatively small external couplingforce for eillciently transmitting to the bone the vibratory forcesexerted by the vibratory structure; and means for actuating saidvibratory portions with electric oscillations throughout the principalspeech frequency range for producing corresponding vibrations of saidvibratory portions across the space between said vibratory portions; themass of the driving vibratory portion and. the stiffness of itsresilient junction being so proportioned and so arranged in thevibratory structure that the vibratory system which they `formwith thelarge mass of said body has a resonance fre- Loco quency which gives agood vibratory response in the speech irequencyrange, and that the massci' the resiliently carried driving vibratory portion is sumcientlylarge and subjected by the oscillations to sumcient accelerationrelative to the bone so that the driving vibratory portion exerts on thedriven vibratory portion and therethrough on the boneinertia reactionforces required for inducing intelligible hearing of speech by boneconduction.

19. In a wearable bone conduction hearing aid device, a vibratorystructure designed and arranged to be suiiiciently light and smallforcomfortable and substantially inconspicuous wear coupled to a healinginducing bone lof the massive body surrounding the inner ears of theuser comprising: a driving vibratory portion having a mass greater thanabout four grams, and

smailer than about one hundred and twenty1 grams so that it is only asmall fraction of the mass of said body; a driven bone-couplingvibratory portion having a resilient junction carrying said drivingportion in a vibratory condition and arranged to operatively couple saidsmall-mass driving portion with the large-mass body by the resilientJunction into a vibratory system; said driven vibratory portion forminga part of a wall portion with lateral dimensions of the order of thelateral dimensions of the driving vibralate from the exterior the spaceacross which said vibratory portions vibrate; the mass of the drivingvibratory portion and thel stillness of its resilient junction being soproportioned and so arranged in the vibratory structure that thevibratory system which they form with the large mass of said body has aresonance frequency which gives a good vibratory response in the speechfrequency range, and that the mass of the resiliently carried drivingvibratory portion is sum4- ciently lage and' subjected by theoscillations to sumcient acceleration relative to the bone so that thedriving vibratory portion exerts on the driven vibratory portion andtherethrough on the bone inertia reaction forces required for inducingintelmass of said body; a driven bone-coupllng vibra-A tory magneticcore member having a resilient Junction carrying said driving coremember in a vibratory condition to form therewith a magnetic pathincluding a gap and arranged to operatively couple said small-massdriving member with the large-mass body by the resilient Junction into avibratoryl system; said driven vibratory portion forming part of asubstantially rigid wall portion with lateral dimensions of the order ofthe lateral dimensions of the driving vibratory portion or greater,sufiiciently large and so .arranged opposite thereto as to maintain saidvibratory unit in a stable-equilibrium coupling position on the boneunder a relatively small external coupling force for emcientlytransmitting to the bone the vibratory forces .exerted by the vibratory`unit; and means including windings for actuating said vibratory coremembers with electric oscillations throughout the principal speechfrequency range for producing corresponding vibrations of said vibratorymembers across said gap; the mass of the driving vibratory member andthe stiffness of its resilient junction being so proportioned and soarranged in the vibratory unit that the vibratory system which they formwith the large mass of said body has a resonance frequency which gives`a good vibratory response in the speech frequency range, and that themass of the resiliently carried diving vibratory member is suf- -cientlylarge and subjected by the oscillations to sutilcient accelerationrelative to the bone so that the driving vibratory member exerts inertiareaction forces required for imparting to the driven vibratory memberand therethrough vto the bone vibrations of large intensity and smallamplitude required for inducing intelligible hearing of speech by boneconduction.

21. In a wearable bone conduction hearing aid device, a vibratory unitdesigned and arranged to be suillciently light and small for comfortableand substantially inconspicuous wear coupled to a hearing inducing boneof the massive body ,surrounding the inner ears of the user comprising:a driving vibratory magnetic core member having a mass greater thanabout four grams, and smaller than about one hundred and twenty grams sothat it is only a small fraction of the mass of said body; a drivenbone-coupling vibratory magnetic core member having a resilient junctioncarrying said driving core member in a vibratory conditionA to formtherewith a magnetic path including a gap and arranged to operativelycouple said small-mass driving member with the large-mass body by theresilient junction into a vibratory system; said driven vibratoryportion forming part of a substantially rigid wall portion with lateraldimensions of the order of the lateral dimensions of the drivingvibratory portion or greater, sufiiciently large and so arrangedopposite thereto as to maintain said vibratory unit in astable-equilibrium coupling position on the bone under a relativelysmall external coupling force for emciently transmitting to the bone thevibratory forces exerted by the vibratory unit; andmeans includingwindings for actuating said vibratory core members with electricoscillations throughout the principal speech` frequency range forproducing corresponding vibrations of said vibratory members across saidgap; said vibratory unit having a closure portion arranged toprotectively isolate from the exterior the space` across which saidvibratory members vibrate; the mass of the driving vibratory member andthe stiffness of its resilient junctionbeing so proportioned and soarranged in the vibratory unit that the vibratory system which they formwith the large mass of said body has a resonance frequency which gives agood vibratory response in the speech frequency range, and that the massof the resilientiy carried driving vibratory member is suillcientlylarge and subjected by the oscillations to sumcient accelerationrelative tb the bone so that the driving vibratory member exerts inertiareaction forces required for imparting to the driven vibratory memberand therethrough to the bone vibrations of large intensity and smallamplitude required for inducing intelligible hearing of speech by boneconduction.

22. In a wearable bone conduction hearing aid device, a vibratorystructure designed and arranged to be suillciently light and small forcomortable and substantially inconspicuous wear coupled to a hearinginducing bone of the massive body surrounding the inner ears of the usercomprising: a driving vibratory portion having a mass greater than aboutfour grams, and smaller than about one hundred grams so that it is onlya small fraction of the mass of said body: a driven bone-couplingvibratory portion having a resilient junction carrying said drivingportion in a vibratory condition and arranged to operatively couple saidsmall-mass driving portion-with the large-mass body by the resilientjunction into a vibratory system; said driven vibratory portion forminga part of a wall' portion with lateral dimensions of the order of thelateral dimensions of the driving vibratory portion or greater,sumciently large and so arranged opposite thereto as to maintain saidvibratory structure in a stableequilibrium coupling position onthe boneunder a relatively small external coupling force for efficientlytransmitting to the bone the vibratory Vforces exerted by the vibratorystructure; and

means for actuating said vibratory portions with electric oscillationsthroughout the principal speech frequency range for producingcorresponding vibrations of said vibratory portions across the spacebetween said vibratory portions;-

the mass of the driving vibratory portion andv the stiness of itsresilient junction being so proportioned and so arranged in thevibratory structure that the vibratory system which they form with thelarge mass o! said body has a resonance frequency which gives a goodvibratory response in the speech frequency range. and that the mass ofthe resiliently carried driving vibratory portion is sufllciently largeand subjected by the oscillations to sumcient acceleration relative tothe bone so that the driving vibratory portion exerts on the drivenvibratory portion and therethrough on the bone inertia reaction forcesrequired for inducing intelligible hearing of speech by bone conduction.

23. The method of enabling a deafened person to hear speech through boneconduction by imparting audio-frequency vibrations to a bone of themassive head body surrounding his inner ears which resides'in soresiliently carrying in a vibratory condition and in astable-equilibrium coupling position on the bone a vibratory portionhaving a mass that is smaller than about one hundred and twenty gramsand only a small fraction of the mass oi' the head body but greater thanabout four grams that the large mass of the body and the small mass ofthe resiliently carried vibratory portion form a vibrating system havinga resonance frequency which gives a good response in the speechfrequency range, and accelerating the resiliently carried vibratoryportion relative to the bone with electric oscillations of the principalspeech frequency range so as to produce by the acceleration of theresiliently carried vibratory mass portion inertia reaction forces whichimpart to the bone the vibratory energy required for conductingcorresponding vibrations ot relatively large intensity and smallamplitude through the bones to the inner ear and induce intelligiblehearing of the speech.

24; The method of enabling a deafened person to hear speech through boneconduction by imparting audio-frequency vibrations to a bone of themassive head body surrounding his inner ears which resides in soresiliently carrying in a vibratory condition and in astable-equilibrium coupling position on the bone a vibratory portionhaving a mass thatV is smaller than about sixty grams and only a smallfraction of the mass of the head body but greater than about four gramsthat the large mass .of the body and the small mass of the resilientlycarried vibratory portion form a vibrating system having a resonancei'requency which gives a good response in the speech frequency range,and accelerating the resiliently carried vibratory portion relative tothe bone with electric oscillations of the principal speech i'requencyrange so as to produce by the acceleration of the resiliently carriedvibratory mass portion inertia reaction forces which impart to the bonethe vibratory energy required for conducting corresponding vibrations oirelatively large intensity and small amplitude through the bones to theinner ear and induce intelligible hearing of the speech.

25. In a wearable bone conduction hearing aid device, a vibratory unitdesigned and arranged to be suihciently light and small for comfortableand substantially inconspicuous wear coupled to a hearing inducing boneoutside the ear canal oi' the massive body of the head surrounding theinner ears of the user comprising: a driving vibratory portion having amass greater than about three grams, which is only a small fraction oi'the mass of said body; a driven bone-coupling vibratory portion having aresilient junction carrying said driving portion in a vibratorycondition, and a substantially rigid contact wall with lateraldimensions of the order of the lateral dimensions of the drivingvibratory portion or greater, sufilciently large and so arrangedopposite thereto as to maintain said vibratory unit in a stable-equilibrium coupling position on the bone under a relatively small externalcoupling force for coupling the small-mass of the driving vibratoryportion with the large-mass body by the resilient junction into avibratory system and for emciently transmitting to the bone thevibratory forces exerted by the vibratory unit; and means for actuatingsaid vibratory portions with electric oscillations throughout theprincipal speech frequency range for producing corresponding vibrationsof said vibratory portions across the f space between said vibratoryportions; the mass of the driving vibratory portion and the stiffness ofits resilient junction being so proportioned and so arranged in thevibratory unit that the vibratory system which they form with the massof said body has a resonance frequency which gives a good vibratoryresponse in the speech frequency range, and that the mass of theresiliently carried driving vibratory portion is sufficiently large andsubjected by the oscillations to sufficient acceleration relative to thebone so that thedriving vibratory portion exerts inertia reaction forcesin a general direction toward the contact wall surface required forimparting to the driven vibratory portion and therethrough to the bonevibrations oi' large intensity and small amplitude required for inducingintelligible hearing of speech by bone conduction.

26. In a wearable bone conduction hearing aid device. a vibratory unitdesigned and arranged to be suillcientiy light and small for comfortableand substantially inconspicuous wear coupled to a hearing inducing boneoutside the ear canal of the massive body of the head surrounding theinner ears of the user comprising: a driving vibratory portion having amass greater than about three grams, which is only a small fraction ofthe mass of said body; a driven bone-coupling vibratory portionr havinga resilient junction carrying said driving portion in a vibratorycondition, and a substantially rigid contact wall with lateraldimensions of the order of the lateral dimensions of the drivingvibratory portion or greater, sufciently large and so arranged oppositethereto as to maintain said vibratory unit in a stableequilibrlumcoupling position on the bone under a relatively small external couplingforce for coupling the small-mass of the driving vibratory portion withthe large-mass body by the resilient junction into a vibratory systemand for emciently transmitting to the bone the vibratory forces exertedby the vibratory unit; and means for actuating said vibratory portionswith electric oscillations throughout the principal speech frequencyrange for producing corresponding vibrations oi' said vibratory portionsacross the space between said vibratory portions: said vvibratory unithaving a closure portion arranged to protectively isolate from theexterior the space across which said vibratory portions vibrate; themass of the driving vibratory portion and the stiness of its resilientjunction being so proportioned and so arranged in the vibratory unitthat the vibm tory system which they form with the mass of said body hasa resonance frequency which gives a good vibratory response in thespeech frequency range. and that the mass of the resiliently carrieddriving vibratory portion is sufilciently large and subjected by theoscillations to sumcient acceleration relative to the bone so that thedriving vibratory portion exerts inertia reaction forces in a generaldirection toward the contact wall surface required for imparting to thedriven vibratory portion and therethrough to the bone vibrations oflarge intensity and small amplitude required for inducing intelligiblehearing of speech by bone conduction.

27. In a wearable bone conduction hearing aid device, a vibratory unitdesigned and arranged to be suillciently light and small for comfortableand substantially inconspicuous wear coupled to a hearing inducing boneoutside the earcanal of the massive body of the head surrounding theinner ears of the user comprising:A a driving vibratory portionhaving amass greater than about three grams, which is only a small fraction ofthe mass of" said body; a driven bone-coupling vibratory portion havinga resilient junction carrying said driving portion in a vibratorycondition, and a substantially rigid contact wall with lateraldimensions of the order of the lateral dimensions of the drivingvibratory portion or greater, sufllciently large and so arranged opposite thereto as to maintain said vibratory unit in a stable-equilibriumcoupling position on the bone under a relatively small external couplingforce for coupling the'small-mass oi the driving vibratory portion withthe large-mass body by the resilient junction into a vibratory systemand for emciently transmitting to the bone the vibratory forces exertedby the vibratory unit: and means for actuating said vibratory portionswith electric oscillations throughout the principal speech frequencyrange for producing corresponding vibrations of saidy vibratory portionsacross the space between said vibratory portions; the mass of thedriving vibratory portion and the stiffness of its resilient junctionbeing so proportioned and so arranged in the vibratory unit that thevibratory system which they form with themassofsaidbodyhas a resonancefrequency which gives a good vibratory response in the speech frequencyrange, and that the mass of the resiliently carried driving vibratoryportion is su'fficiently large and subjected by the oscillations tosuillcient acceleration relative to the bone so that the drivingvibratory portion exerts inertia reaction forces required for impartingto the driven vibratory portion and therethrough to the bone vibrationsof large intensity and small amplitude required for inducingintelligiblehearlns of speech by bone conduction. and externalsupporting means having a universal Joint connection with said vibratoryunit for holding said contact coupled to the bone.

28. In a wearable bone conduction hearing ai device, a vibratory unitand arranged to be sufiiciently light and small for comfortable andsubstantially inconspicuous wear coupled to a hearing inducing bone ofthe massive body surrounding the inner ears of the user comprising: adriving vibratory portion 'havinga' mass greater than about four grams,'and smaller than about eighty grams so that it is only a small fractionof the mass of said body; a driven bone-coupling vibratory portionhaving a resilient junction carrying said driving portion in a vibratorycondition and arranged to operatively couplesaid smallmass drivingportion with the large-mass body by the resilient junction into avibratory system; said driven vibratory portion 'forming a part of awall portion suillciently extended and so arranged under and relativelyto the driving vibratory portion as tomaintain said vibratory unit in astableequilibrium coupling position on the bone under a relatively smallexternal coupling force for eiliciently transmitting to the bone thevibratory forces exerted by the vibratory unit; and means for actuatingsaid vibratory portions with electric oscillations throughout theprincipal speech ,irequency range for producing corresponding vibrationsof said vibratory portions across the space between said vibratoryportions; the mass of the driving vibratory portion and the of itsresilient junction being so proportioned and so arranged in thevibratory unit that`the vibratory system which they form with the largemass of said body has a resonance frequency which gives a good vibratoryresponse in the speech frequency range, and that the mass of theresiliently carried driving vibratory portion is sumciently large andsubjected by the oscillations to suilicient acceleration relative to thebon'e so that the driving vibratory portion exerts inertia reactionforces required for l imparting to 'f the driven lvibratory portion andtherethrough to the bone vibrations of large intensity and smallamplitude required for inducing intelligible hearing of speech by boneconduction. 1 i

29. 1n a wearable bone conduction hearing aid device, a vibratory. unitdesisned and arranged to be sufilciently light and small for comfortableand substantially incons'picuous wear coupled to a hearing inducing boneof the massive body surrounding the inner ears of the user comprising: adriving vibratory portion having a mass greater than about four grams.and smaller than about iiftygramasothatitisonlyas'mallfractionof themass of said body; a driven bone-coupling vibratory portion having aresilient junction carrying said driving portion in a vibratorycondition and arranged to operatively couple said small-mass drivingportion with the large-mass body by the resilient junction into a.vibratory system; said driven vibratory portion forming a part of a wallportion sufliciently extended and so arranged under and relatively tothe driving vibratory portion as to maintain said vibratory unit in astable-equilibrium coupling position on the bone under a relativelyVsmall external coupling force for actuating said vibratory portionswith electric oscillations throughout the principal speech frequencyrange for producing corresponding vibrations of said vibratory portionsacros -the space between said vibratory portions; the

mass of the driving vibratory portion and the stillness of its resilientjunction being so proportioned and so arranged in the vibratory unitthat the vibratory systemA which they form with the massv of said bodyhas a resonance frequency which gives a good vibratory response in thespeech frequency range, and that the mass of the resiliently carrieddriving vibratory portion is sumciently large and subjected by theoscillationsto suilicient acceleration relative to the bone so that thedriving vibratory portion exerts on the driven vibratory portion andtherethrough on the bone inertia reaction forces required for inducingintelligible hearing of speech by bone conduction.

30. Inla wearable bone'conduction hearing aid device, a vibratorystructure designed and arranged to be suiilcientlyiight and small forcomfortable and substantially inconspicuous wear coupled to a hearinginducing bone of the massive body surrounding theinner ears oi' the usercomprising: a driving vibratory portion having a mass greater than aboutfour grams, and smaller thanaboutthirtygramssothatitisonlya smallfraction of the mass of said body; a driven bone-coupling vibratoryportion having a resilforming a part of a wall portion with lateral dilmensions of the order of the lateral dimensions of the driving vibratoryportion or greater, suiiiciently large and so arranged opposite theretoas to maintain said vibratory structure in a stableequilibrium couplingposition on the bone under a relatively small external coupling forcefor eiliciently transmitting to the bone the vibratory forces exerted bythe vibratory structure; and means for actuating said vibratory portionswith electric oscillations throughout the principal speech frequencyrange for producing corresponding vibrations of said vibratory portionsacross the space between said vibratory portions; the mass of thedriving vibratory portion and the stiffness of its resilient junctionbeing so proportioned and so arranged in the vibratory structure thatthe vibratory system which they form with the large mass of said bodyhas a resonance frequency which gives a good vibratory response in thespeech frequency range, and that the mass of the resillently carrieddriving vibratory portion -is suillciently large and subjected by theoscillations to sufcient acceleration relative to the bone so that thedriving vibratory portion exerts on the driven vibratory portion andtherethrough on the bon'e inertia reaction forces required for in-`ducing,` intelligible ,y hearing of vspeech by bone conduction.

31. Ina wearable bone conduction hearing aid device. a vibratory unitdesigned and arranged to be suillciently Y light and for comfortable andsubstantially inconspicuous wear coupled to a hearing inducing boneoutside the ear canal of the massive body of the head surrounding theinner ears of thequ'ser comprising: ardriving vibratory portion having amass greater than about three grams, which is only a small fraction ofthe f mass of said body; a driven bone-coupling vibratory. portionhav-inge. resilient junction carrying said driving portion ln ayvibratory condition, and a substantially rigid contact wall withlateral dimensions of the order of the lateral dimensions of thedrivingrvibratory portion or greater, sumciently large and so arrangedopposite thereto as to maintain said vibratory unit in astableequilibrium coupling position on the bone under a relatively smallexternal coupling force for coupling the small-mass of the drivingvibratory portion with the large-mass body by the resilient junctioninto a vibratory system and for elciently transmitting to the bone thevibratory forces exerted by the vibratory unit; and means for actuatingsaid vibratory portions with electric oscillations throughout theprincipal speech frequency range for producing corresponding vibrationsof said vibratory portions across the space between said vibratoryportions; the mass of the driving vibratory portion and the stiffness ofits resilient junction being s o proportioned and so arranged in thevibratory unit that the vibratory system which they form with the massof said body has a resonance frequency which gives a. good vibratoryresponse in the speech frequency range, and that the maas of theresiliently carried driving vibratory portion is sumciently large andsubjected by the oscillations to suilcient acceleration relative to thebone so that the driving vibratory portion A exerts inertia reactionforces in a general direction toward the contact wall surface requiredfor imparting to the driven vibratory portion and therethrough to thebone vibrations of large intensity and smallamplitude required forinducing intelligible hearing of speech by bone conduction, and externalsupporting means having a pivotal joint connection with said vibratoryunit for holding said contact wall coupled to the bone.

32. In a wearable bone conduction hearing aid device, a vibratorystructure designed and arranged to be suillciently light and small forcomfortable and substantially inconspicuous wear coupled to a hearinginducing bone outside the ear canal of, the massive body of the headsurrounding the inner ears of the user comprising: a driving vibratoryportion having a mass greater than about four grams, and smaller thanabout one hundred and twenty grams so that it is only a small fractionof the mass of said body; a driven bone-coupling vibratory portionhaving a resilient junction carrying said driving portion in a vibratorycondition and arranged to operatively couple said small-mass drivingportion with the largemass-body by the resilient junction into avibratory system; said driven vibratory portion forming a part of a wallportion with lateral dimensions of the order ol' the lateral dimensionsof the driving vibratory portion or greater, sumciently large and soarranged opposite thereto as to maintain said vibratory structure in astable-equilibrium coupling position on the bone tory forces exerted bythe vibratory structure; and means tor actuating said vibratory portionswith electric oscillations throughout the principal speech frequencyrange for producing corresponding vibrationsoi' said vibratory portionsacross the space'between said vibratory portions; the mass of thedriving vibratory portion and the stiness of its resilient junctionbeing so proportioned and so arranged in the vibratory strucf ture thatthe vibratory system which they form with the large mass of said bodyhas a resonance frequency which gives a good vibratory response in thespeech frequency range, and that the mass of the resiliently .carrieddriving vibratory portion is suiiiciently large and subjected by theoscillations to suiiicient acceleration relative to the bone so that thedriving vibratory portion exerts on the driven vibratory portion andtherethrough on the bone inertia reaction forces required for inducingintelligible hearing of speech by bone conduction, and externalsupporting means having a pivotal ioint connection with said vibratorystructure for holding said wall portion cooperatively coupled to thebone.

33. In a wearable bone conduction hearing aid device, a vibratory unitdesigned and arranged to be sumciently light and small for comfortableand substantially inconspicuous wear coupled to a hearing inducing boneoutside the ear canal of the massive body of the head surrounding theinner ears oi the user comprising: a driving vibratory portion having amass greater than about i'oury grams, and smaller than about two hundredBrains so that it is only a small fraction of the mass of said body; adriven bone-coupling vibratory portion having a resilient junctioncarrying said driving portion in a vibratory condition and arranged tooperatively couple said smallmass driving portion with the large-massbody by the resilient junction into a vibratory system; said vibratoryunit having a'substantlally rigid wall portion suiiiciently large and soarranged under and relatively to the .driving vibratory portion as tomaintain said vibratory unit in a stableequilibrium coupling position onthe bone under a relatively small external coupling force for emcientlytransmitting to the b one the vibratory forces exerted by the vibratoryunit; and means for actuating said vibratory portions with electricoscillations throughout the principal speech frequency range forproducing corresponding vibrations oi said vibratory portions across thespace between said vibratory portions; the mass of the driving vibratoryportion and the stiffness of its resilient junction being soproportioned and so arranged in the vibratory unit that the vibratorysystem which they form with the mass oi' said body has a resonancefrequency which gives a good vibratory response in the speech frequencyrange, and that the mass of the resiliently carried driving vibratoryportion is sufficiently large and subjected by the oscillations tosufficient acceleration relative to the bone so that the drivingvibratory portion exerts on the driven vibratory portion andtherethrough on the bone inertia reaction forces required for inducingintelligible hearing of sp'eech by bone conduction, and externalsupporting means having a universal joint connection with said vibratoryvunit for holding said wall portion cooperatively coupled to the bone.

34. In a. wearable bone conduction hearing aid device, a vibratory unitdesigned and arranged to be sumciently light and small for comfortableand substantially inconspicuous wear coupled to a hearing inducing boneoutside the ear canal of the massive body of the head surrounding theinner ears of the user comprising: a driving vibratory portion having amass greater than about three grams, which is only a small fraction ofthe mass of said body; a driven bone-coupling vibratory portion having aresilient junction carrying said driving portion in a vibratorycondition. and a substantially rigid contact wall with lateraldimensions of the order of the lateral dimension of the drivingvibratory portion or greater, sumciently large and so arranged oppositethereto as to maintain said vibratory unit in a stable-equilibriumcoupling position on the bone under a relatively small external couplingforce for coupling the small-mass of the driving vibratory portion withthe large-mass body by the resilient junction into a vibratory systemand for emciently transmitting to the bone the vibratory forces exertedby the vibratory unit; and means for actuating said vibratory portionswith electric oscillations throughout the principal speech frequencyrange for producing corresponding vibrations of said vibratory portionsacross the space between said vibratory portions; the mass oi' thedriving vibratory portion and the stiii'ness of its resilient junctionbeing so proportioned and so arranged in the vibratory unit that thevibratory system which they form with the mass of said body has aresonance frequency which gives a good vibratory response in the speechfrequency range, and that the mass oi the resiliently carried drivingvibratory portion is sufficiently large and subjected by theoscillations to suflicient acceleration relative to the bone so that thedriving vibratory portion exerts inertia reaction forces in a generaldirection toward the contact wall surface required for imparting to thedriven vibratory portion and therethrough to the bone vibrations oflarge intensity and small amplitude required for inducing intelligiblehearing, of speech bybone conduction, said contact wall being part of acasing enclosing said driving vibratory portion.

35. In a wearable bone'oonduction hearing aid device. a vibratory unitdesigned and arranged to be sumciently light and small for comfortableand substantially inconspicuous wear coupled to a hearing inducing boneof the massive body surf rounding the inner ears of the user comprising:a, driving vibratory magnetic core member having a mass greater thanabout four grams, and smaller than about sixty grams so that it is onlya small fraction of the mass of said body; a driven bone-couplingvibratory magnetic core member having a resilient junction carrying saiddriving core member in a vibratory condition to form therewith amagnetic path including a, gap and arranged to operatively couple saidsmall-mass driving member with the large-mass body by the resilientjunction into a vibratory system; said driven vibratory member formin apart of a wall portion suiliciently extendedl and sofarranged under andrelatively to the driving vibratory member as to maintain said vibratoryunit in a stableequilibrium coupling position on the bone under arelatively small external coupling force for emciently transmitting tothe bone the vibratory forces exerted by the vibratory unit; and meansincluding windings for actuating said vibratory core members withelectric oscillations throughout the principal speech frequency rangefor producing corresponding vibrations of ysaid vibratory members acrosssaid gap; the mass of the driving vibratory member and the stillness ofits resilient junction being so proportioned and so arranged in thevibratory unit that the vibratory system which theyformwiththemassofsaidbodyhasaresonance frequency which gives a good vibratoryresponse in the'speech frequency range. and that the mass of theresiliently carried driving vibra.-

tory member is sumciently large and subjected by the oscillations tosufllclent acceleration relative to the bone so that the drivingvibratory member exerts on the driven vibratory member and therethroughon the bone inertia reaction forces required for inducing intelligiblehearing of speech by bone conduction.

36. In a wearable bone conduction hearing aid device a vibratory unitdesigned and arranged to be sufficiently light and small for comfortableand substantially inconspicuous wear coupled to a hearing inducing boneof the massive body surrounding the inner ears of the user comprising: adriving vibratory magnetic core member having a mass greater than aboutfour grams, and smallerv than about forty grams so that it is onlyasmall fraction of the mass of said body; a driven bone-couplingvibratory magnetic core member having a resilient junction carrying saiddriving core member in a vibratory condition to form therewith amagnetic path including a gap and arranged to operatively couple saidsmall-mass driving member with the large-mass body by the resilientjunction into a vibratory system; said driven vibratory member forming apart of a wall portion sufliciently extended and so arranged -under andrelatively to the driving vibratory member as to maintain said vibratoryunit in a stable-equilibrium coupling potion on the bone under arelatively small external coupling force for eiiiciently transmitting tothe bone the vibratory forces exerted by the vibratory unit; and

` means including windings for actuating said vispeech frequency range,and that the mass of the resiliently carried driving vibratory member issumciently large and subjected by the oscillations to suilicientacceleration relative to the bone so that the driving vibratory memberexerts inertia reaction forces required for imparting to the drivenvibratory member and therethrough to f the bone vibrations of largeintensity and small amplitude required for inducing intelligible hearingof speech by bone conduction.

37. In a wearable bone conduction hearing aid device, a vibratory unitdesigned and arranged to be sumciently light and small for comfortableand substantially inconspicuous wear coupled to a hearing inducing boneof the massive body surrounding the inner ears of the user comprising: adriving vibratory magnetic core member having a mass greater than aboutfour grams, and smaller than about two hundred grams so that it is onlya small fraction of the mass of said body; a driven bone-couplingvibratory magnetic core member having a resilient junction carrying saiddriving core member in avibratory condition to form therewith a magneticpath including a gap and arranged `to operatively couple said smallmassdriving member with the large-mass body by the resilient junction into avibratory system;

said vibratory unit having a substantially rigid wall portionsufliciently large and so arranged under and relatively to the drivingvibratory member as to maintain said vibratory unit in astableequilibrium coupling position on the bone under a relatively smallexternal coupling force for eiilciently transmitting to the bone thevibratory forces exerted by the vibratory unit; and means includingwindings fbr' actuating said vibratory core members with electricoscillations throughout the principal speech frequency range forproducing corresponding vibrations of said vibratory members across saidgap; the mass of the driving vibratory member and the stiffness of itsresilient junction being so proportioned and so arranged in thevibratory unit that the vibratory system which they form with the massof said body has a resonance frequency which gives a good vibratoryresponse in the speech frequency range, and that the mass of theresiliently carried driving vibratory member is sufiiciently large andsubjected by the oscillations to sumcient acceleration relative to thebone so that the driving vibratory member exerts on the driven vibratorymember and therethrough on the bone inertia reaction forces required forinducing intelligible hearing of speech by bone conduction, said wallportion forming a part of a casing enclosing said driving vibratorymember.

38. In a wearable bone conduction hearing aid device, a vibratory unitdesigned and arranged to be sufllciently light and small for comfortableand substantially inconspicuous wear coupled to a hearing inducing boneof the massive body surrounding the inner ears of the user comprising: adriving vibratory portion having a mass greater than about four grams,and smaller than about two hundred grams so that it is only a smallfraction of the mass of said body; a driven bonecoupling vibratoryportion having a resilient junction carrying said driving portion in avibra' tory condition and arranged to operatively couple said small-massdriving portion with the largemass body by the resilient junction into avibratory system; said vibratory unit having a substantially rigid wallportion suiliciently large and so arranged under and relatively to thedriving vibratory portion as to maintain said vibratory unit in astable-equilibrium coupling position on the bone under a relativelysmall external coupling force for efficiently transmitting to the bonethe vibratory forces exerted by the vibratory unit; and means foractuating said vibratory portions with electric oscillations throughoutthe principal speech frequency range for producing correspondingvibrations of said vibratory portions across the space between saidvibratory portions; the mass of the driving vibratory portion and thestiffness of its resilient junction being so proportioned and soarranged in the. vibratory unit that the vibratory system which theyform with the mass of said body has a resonance frequency which gives agood vibratory response in the speech frequency range, and that the massof the resiliently carried driving vibratory portion is suflilcientlylarge and subjected by the oscillations to sufcient accelerationrelative to the bone so that the driving vibratory portion exerts on thedriven vibratory portion and therethrough on the bone inertia reactionYforces required for inducing intelligible hearing of speech by boneconduction, said wall portion forming a part of a casing enclosing saiddriving vibratory portion.

39. In a wearable bone conduction hearing aid ranged to be sufllclentlylight and small for comfortable and substantially inconspicuous wearcoupled to a hearing 'inducing bone of the massive body surrounding theinner ears of the user comprising: a driving vibratory portion having amass greater` than about four grams, and smaller than about one hundredand twenty grams so that it is only a small fraction of the mass of saidbody; a driven bone-coupling vibratory portion having a resilientjunction carrying said driving portion in a vibratory condition andarranged to operatively couple said small-mass driving portion with thelarge-mass body by the resilient junction into a vibratory system; saiddriven vibratory portion forming a part of a wall portion with lateraldimensions of the order of the lateral dimensions of the drivingvibratory portion or greater, sufllciently large and so arrangedopposite thereto as to maintain said vibratory structure in a istable-equilibrium coupling position on the bone under a relativelysmall external coupling force for eihciently i transmitting to the bonethe vibratory forces exerted by the vibratory structure; and means foractuating said vibratory portions with electric oscillations throughoutthe principal speech frequency range for producing correspondingvibrations of said vibratory portions across. the

space between said vibratory portions; the mass of the driving vibratoryportion and the stiffness of its resilient junction being soproportioned andso arranged in the vibratory structure that thevibratory system which they form with the large mass of said body has aresonance frequency which gives a good vibratory response in the speechfrequency range, and that the mass of the resiliently carried drivingvibratory portion is sumciently large and subjected by the oscillationsto suihcient acceleration relative to the bone so that the drivingvibratory portion exerts on the driven vibratory portion and there'-through on the boneinertia reaction forces required for inducingintelligible hearing of speech by bone conduction, said wall portionforming a part of a casing enclosing said driving vibratory portion.

40. In a wearable bone conduction hearing aid device, a vibratory unitdesigned and arranged to be suiiiciently light and small for comfortableand substantially inconspicuous Wear coupled to a hearing inducing boneof the massive body surrounding the inner ears of the user comprising: adriving vibratory portion having a mass greater than about four grams,and smaller than about eighty grams so that it is only a small fractionof the mass of said body; a driven bone-coupling vibrato-ry portionhaving a resilient junction carrying said driving portion in a vibratorycondition and arranged tooperatively couple said small-mass drivingportion with the:

large-mass body by the resilient junction into a vibratory system; saiddriven vibratory portion I forming a. part of a wall portionsutliciently extended and soarranged under and relatively to 4thedriving vibratory portion as to maintain said vibratory unit in`astable-equilibrium coupling position on the bone under a relativelysmall external coupling force for eiliciently transmitting to the bonethe vibratoryforces exerted by the vibratory unit; and means foractuating said vibratory portions with electric oscillations throughoutthe principal speech frequency range for producing correspondingvibrations of said vibratory portions across the space between saidvibratory portions; the mass of. the driving vibratory portion and thestiffness of its resilient junction being so proportioned and soarranged in the vibratory unit that the vibratory system which they formwith the large mass of said body has a resonance frequency which givesagood vibratory -response in the speech frequency range, and 'that themass of the resiliently car-` rled driving vibratory portion issufficiently large and subjected by the oscillations to sumcientsceeleration relative to the bone so that the driving vibratory portionexerts inertia reaction forces required for imparting to the drivenvibratory portion and therethrough to the bone vibrations of largeyintensity and small amplitude required for inducing intelligible hearingof speech by bone conduction, said wall portion forming a part of acasing enclosing said driving vibratory portion.

41. In a wearable bone conduction hearing aid device, a vibratorystructure designed and arranged to be sufficiently light and small forcomfortable and substantially inconspicuous wear coupled to a hearinginducing bone of the massive body surrounding the inner ears of the usercomprising: a driving vibratory portion having a mass greater than aboutfour grams, and smaller than about eighty grams so that it is only asmall fraction of the mass of said body; a driven bonecoupling vibratoryportion having a resilient junction carrying said driving portion in avibratory condition and arranged to operatively couple said small-mass'driving portion with the largemass body by the resilient junction intoa vibratory system: said driven vibratory portion forming a part of awall portion with lateral dimensions of the order of the lateraldimensions of the driving vibratory portion or greater, sutllcientlylarge and so arranged opposite thereto as to maintain said vibratorystructure in a stableyequilibrium coupling position on the bone under arelatively small external coupling force for efficiently transmitting tothe bone the vibratory forces exerted by the vibratory structure; andmeans for actuating said vibratory portions with electric oscillationsthroughout the principal speech frequency' range for producingcorrespending vibrations oi' said vibratory portions across the spacebetween said vibratory portions; the mass of the driving vibratoryportion and the stiffness of its resilient junction being soproportioned and so arranged in the vibratory structure that thevibratory system which they form with the large mass of said body has aresonance frequency which gives a good vibratory response in the speechfrequency range, and that the mass of the resillently carrieddrivingvibratory portion is sumciently large and subjected by theosciliations to sumcientacceleration relative to the bone so that thedriving vibratory portion exerts on the driven vibratory portion andtherethrough on the bone inertia reaction forces required for inducingintelligible hearing of speech by bone conduction, said wall portionforming a part of a casing enclosing said driving vibratory portion.

42. In a wearable bone conduction hearing aid device, a vibratory unitdesigned and arranged to be suiliclently light and small for comfortableand substantially inconspicuous wear coupled to a hearing inducing-boneof the massive body surrounding the inner ears of the user comprising: adriving vibratory magnetic core member having a. mass greater than aboutfour grams, and smaller than about one hundred and twenty grams so thatit is only a. small fractionof the mass of said body: a drivenbone-coupling vibratory magnetic core `member having a resilientjunction carrying said driving core member in a vibratory condition toform therewith a magnetic path including a gap and arranged tooperatively couple said smallmass driving member with the large-massbody by the resilient junction into a vibratory system; said drivenvibratorymember forming a part of a wall portion sufficiently extendedand so arranged under and relatively to the driving vibratory member asto maintain said vibratory unit in a stable-equilibrium couplingposition on the bone `under a relatively small external coupling forcefor efliciently transmitting to the bone the vibratory forces exerted bythe vibratory unit: and means including windings for actuating saidvibratory core members with electric oscillations throughout theprincipal speech frequency range for producing corresponding vibrationsof saidvibratory members across said gap; the mass of the drivingvibratory member and the stiffness of its resilient junction being soproportioned and so arranged in the vibratory unit that the vibratorysystem which they form with the large mass of said bodyV has a resonancefrequency which gives a good vibratory response in the speech frequencyrange, and that the mass of the resiliently carried driving vibratorymember is sufficiently large and subjected by 'the oscillations tosumcient acceleration relative to the bone so that,

surrounding the inner ears of the user compris-v ing: a drivingvibratory magnetic core member having a mass greater than about fourgrams,'

and smaller than about sixty grams so that it is only a small fractionof the mass of said body; a driven bone-coupling vibratory magnetic coremember having a resilient junction carrying said driving core member ina vibratory condition to form therewith a magnetic path including a gapand arranged to operatively couple said small-mass driving member withthe large-mass body by the resilient junction into a vibratory system;saidv driven vibratory member forming a part of a-wallportionsuillciently extended and so arranged under and relatively to thedriving vibratory member as to maintain said vibratory ,unit in astable-equilibrium coupling position on the bone under a relativelysmall external coupling force for eiilciently `transmitting to the bonethe vibratory forces exerted by the vibratory unit; and means includingwindings for actuating said vibratory core members with electricoscillations throughout the principal speech frequency range forproducing corresponding vibrations of said vibratory members across saidgap; the mass of the driving vibratory member and the stiffness of itsresilient junction being so proportioned and so arranged in thevibratory unit that the vibratory system which they form with the massof said body has aresonanoe' frequency which gives a good vibratoryresponse quired for inducing intelligible hearing of speech by boneconduction, said wall portion forming a part of a casing enclosing saiddriving vibratory member.

44. In a wearable bone conduction hearing ald device, a vibratory /unitdesigned and arranged to be suiliciently light and small for comfortableand substantially inconspicuous Wear coupled to a hearing inducing boneof the massive body surrounding the inner ears of the user comprising: adriving vibratory magnetic core member having a mass greater than aboutfour grams. and smaller than about two hundred grams so that it is onlya small fraction of the mass of said body; a driven bonecouplingvibratory magnetic core member having a resilient junction carrying saiddriving core member l'n a vibratory condition to form therewith amagnetic path including a gap and arranged to operatively couple saidsmall-mass driving member with the large-ma body by the resilientJunction into a vibratory System: said vibratory unit having asubstantially rigid wall portion sumciently large and so arranged underand relatively to the driving vibratory member as to maintain saidvibratory unit in a stable-equilibrium coupling position on the boneunder a relatively small external coupling force for efficientlytransmitting to the bone the vibratory forces exerted by the vibratoryunit; and means including windings on the driving core member foractuating said vibratory core members with electric oscillationsthroughout the principal speech frequency range for producingcorresponding vibrations of said vibratory members across said gap; 4themass of the driving vibratory member and the stiffness of its resilientJunction being so proportioned and so arranged in the vibratory unitthat the vibratory system which they form with the mass of said body hasa resonance frequency which gives a good vibratory response in thespeech frequency range, and that the mass of the resiliently carrieddriving vibratory member is sufllciently large and subjected bytheoscillations to sumcient acceleration relative to the bone so that thedriving vibratory member exerts on the driven vibratory member andtherethrough on the bone inertia reaction forces required for inducingintelligible hearing of speech by bone conduction.

45. In a wearable bone conduction hearing aid device, a vibratory unitdesigned and arranged to be suillciently light and small for comfortableand substantially inconspicuous wear coupled to a hearing inducing boneof the massive body surrounding the inner ears of the user comprising:

a driving vibratory magnetic core member having a mass greater thanabout four grams, and smaller than about one hundred and twenty grams sothat it isonly a small fraction of the mass of said body a drivenbone-coupling vibratory magnetic core member having a. resilientJunction carrying said driving core member in a yvibratory system; saiddriven vibratory portion forming part of a substantially rigid wallportion

